class Thing:
def __init__(self):
self.num = 21
def double(foo):
foo.num = foo.num * 2
thing = Thing()
double(thing)
print thing.num
Y2xhc3MgVGhpbmc6CglkZWYgX19pbml0X18oc2VsZik6CgkJc2VsZi5udW0gPSAyMQoKZGVmIGRvdWJsZShmb28pOgoJZm9vLm51bSA9IGZvby5udW0gKiAyCgp0aGluZyA9IFRoaW5nKCkKCmRvdWJsZSh0aGluZykKCnByaW50IHRoaW5nLm51bQ==